Contents: 1. Information 2. Bosch “small” 80 mm

Contents: 3. Bosch “big” 90 mm4. Bosch prices

1. Information

Welcome. The magneto has two separate functions, 1) produce sparks for ignition, 2) produce electric power for lights.

1) Ignition Pulses: The magneto produces precisely timed pulses, which are transformed into sparks by an internal or external coil.

2) Lights Power: The lights power is normally 6 volts alternating current (6V AC). Normally the correct bulbs are used, and none are burned out. But under certain circumstances the voltage can be less, like 3 volts, or more, like 10 volts. When two or more bulbs share the same generator wire, and one of the bulbs burns out, the others will get an over-voltage, like 8 or 10 volts, become instantly bright and soon burn out. The total watts of the bulbs has to match the watts of the generator, for the voltage to be 6 volts. If the bulb watts is more, then the voltage is less so the light is dim. Bosch makes magnetos with extra generator coils, one for each light, to eliminate the over-voltage and under-voltage problem.

Magneto-Generator History: Moped magnetos changed as moped lights changed over the years. In the 1960’s not many countries worldwide had laws about the brightness of moped lights or the placement of switches and buttons. Mopeds did not have brake lights or extra generator coils for them. A typical 1960’s moped had a 15 watt headlight and a 2 watt tail light, both powered by the same 17 watt generator coil.

Starting in 1972, the USA adopted safety standards for motorcycles and motor-driven cycles (Mopeds had not been defined yet). Lights, rims, brakes and tires had to be US DOT approved. Tail lights had to shine to the sides. Engine stop switches/buttons had to be reachable by the right thumb, while horn and light switches had to be reachable by the left thumb. Switches and fuel petcocks had to be labeled and say what they do. Brake lights were required.

Then in historic 1976 the USA adopted safety standards specifically for mopeds and motorized bicycles. The brake light had to be brighter (at least 10 watts) and not cause the headlight to get dimmer.

Internal and External Ignition Ground: To supply the required independent brake light power, there were two solutions. 1) Internal Ignition Ground, where the ignition source coil internal ground was kept the same, and an extra generator coil was added or 2) External Ignition Ground, where the ignition source coil internal ground was relocated to outside of the engine and used as a brake light power source. Bosch made both magneto types, in both sizes 80 and 90 mm.

Swapping Flywheels: Nearly identical flywheels can have different timing angles. That means the woodruff key groove is at a different angles to the “bump” on the points cam. So you can swap flywheels but your ignition timing would be way off. more to follow…

Over 200 quality Bosch magneto parts attended the reunion.The 80 mm “small” ones are left, the 90 mm “big” ones are right.Not shown, the many engines and bikes the used parts came from.

It don’t come easy. Parts catalogs list the bike maker part numbers, but most do not also give the component maker part number.

Bosch coil part numbers come from the packaging of new coils. Sometimes empty ripped-up original boxes are pieced back together, to get the part number translation, such as Sachs-to-Bosch. 1970’s-80’s armatures also have the last 3 digits stamped on.

Bosch stator part numbers are on the back of the base plate. The first 7 digits are cast in, the same for all. The last 3 digits of the stator assembly part number are stamped on by the factory when the coils are attached.

Bosch stator identification: Each engine has a different and unique rubber grommet for the wires to pass through. A pile of used moped stators can be sorted by grommet type, which is engine type. The ones missing grommets can be matched to the grommet ones by stator part number. This is done without any books or manuals. Specifications, illustrations, or part numbers from books, manuals, internet photos are additional forms of ID. All forms of ID must agree.

2. “Small” Bosch Magnetoswith Ø80 flywheel and Ø80 base plate

80 mm Bosch flywheel uses M22x1.5 puller, M8nut 12-13 hex

80 mm Bosch magnetos have these condensers and points:

2207 013 005late with wire type

2207 013 004early no-wire type

1217 330 035early solder type

2207 330 050late screw-on type

screw-on condensereyelet connectors

1950’s-60’shad solder type condensers and no-wire points. The points-to-condenser wire was sold separately.

1970’s-80’s had screw-on type condensers and with-wire points. No more soldering.

A solder-type can be replaced with a screw-on type, by adding eyelet connectors to the wire ends.

80 mm Bosch armatures (source coils) have 47 mm hole spacing:

1214-210-459

1214-210-460

1214-210-461

1214-210-462

1214-210-463

All of the Bosch magnetos listed below are the internal ignition ground type, unless noted in bright blue.

Sparta stators are 4-wire, 3-coil. Top coils are (behind) ignition (blue wire) and (in front) brake light (green wire and green/black wire). Bottom coil is lights (head light, tail light, speedo light, and horn) (yellow wire). The ignition and light coils are grounded internally. The brake light coil has an external ground. Because of the internal ground on the ignition source coil, the points continuity cannot be checked unless the source coil is disconnected. Bosch has provided a condenser with a screw-on nut with detachable eyelet connector wires, for testing the points for continuity. Otherwise, the ohms of the coil is almost the same as the ohms of the points. See Service/Electrical/Wiring Diagrams/Sparta Foxi for more Sparta wiring info.

This Bosch 2207 031 161 Kreidler stator assembly is the same as a Bosch 2207 031 160 Sachs 504 stator, except for the 1-wire brake light coil. But the flywheel is very different.

Use a 2-wire brake light coil for a Sachs 504, as a substitute for a 1-wire Kreidler type. The additional green/black wire must be grounded to the frame. Because there were 10 times more Sachs 504’s sold in late 1970’s California than Kreidlers, the coils for Sachs are not as scarce.

This 009 flywheel is the same as the more common 002. The lighting coils are different. The lights coil has more windings, and the brake light coil has two wires, green and green/black, instead of just one green wire. This provided power for recharging the turn signal battery without dimming the other lights. Read more in Wirings Gallery, scroll down to “K” Kreidler.

This 2-wire 10W generator armature 1214 210 462 is physically the same as a 2-wire one 1214 210 450, and can be a substitute. When changing from 1 to 2 wires, the additional green/black wire must be grounded to the frame.

3. “Big” Bosch Magnetoswith Ø90 flywheel and Ø90 base plate

90 mm Bosch flywheels use M26x1.5 puller, M10nut 14-17 hex

90 mm Bosch magnetos have these points and condensers:

0217 013 021Laura 48 18 26late type

0217 013 012Laura 48 18 26early type

early plate with post

late plate without post

1950’s-60’s had “early” points, no pivot post. The early pivot post was part of the base plate, but it unscrews.

1970’s-80’s had “late” points, with pivot post. These replace the older points, once the post is removed.

The early and late points have the same Laura part number, because the new parts replace and supersede.

1217 330 035 “short”

1217 330 037 “tall”

eyelet connectors for screw-on condenser

2207 330 050“screw-on”

1950’s-60’s had “short” solder-type condensers, but can have “long”

1970’s-80’s had “short” or “long” solder-type condensers

Either solder-type can be replaced with a screw-on type, by adding eyelet connectors to the wire ends.

90 mm Bosch armatures (source coils) have 54 mm hole spacing:

1214-210-064

1214-210-069

1214-210-490

1214-210-492

1214-210-554

1214-210-555

1214-210-556

1214-210-557

All of the Bosch magnetos listed below are the internal ignition ground type, unless noted in bright blue.

The Sears Allstate Parts Manual is where this specification and illustration are from. It lists the light bulbs: head 6V 15/15W and tail 6V 2.4W, brake 6V 3W. So the magneto rating must be close to 6V 17/3W.

0212 010 001 flywheels: Several individually numbered Bosch magneto flywheels for Sachs 504 engines are offered for sale below. The focus is on the condition of the surface of the points cam. All of the flywheels are otherwise straight and with a good woodruff key groove. The flywheel rotates counter clockwise, viewed from it’s outer facing side. Two views, 180 degrees apart, of each flywheel are shown below. The “A” side is the upwards ramp that opens the points. This is where the most wear occurs, and where the most smoothness and precision are needed, or else the points rubbing block wears down prematurely. The “B” side shows most of the key groove. Any rust has not been cleaned off yet, but is not a problem, other than rust on the outside surface of the points cam.

Flywheel 1: $20The cam has been cleaned. Rust pits visible at the top of the up ramp. Click to enlarge.

Flywheel 2 $80: The cam has been cleaned. Never mind the orange rust. The cam surface is all good on the outboard side of the points rubbing block lane. But it has some pitting near the top of the up ramp on the inboard side of the “lane”.

Flywheel 4 $25: The B side has not been wiped with steel wool yet. The A side has rust pits all across the points “lane”. There is one original smooth area, that is dark from a reflection. The whole cam would need to be grinded down by the same amount to preserve it’s shape. This can be done with little high-speed sanding and polishing drums, but it’s difficult and it comes out a little (or a lot) lumpy.

Flywheel 5 $60: It has not been cleaned yet. Looks like it would “clean up” good, with steel wool, then emery cloth(s) and polishing. Side A shows pits in the middle of the plateau. So the whole cam has to be sanded down evenly, then polished smooth.

Flywheel 6: $150 It has not been cleaned. You can see it’s a new one.

Flywheel 7 N/A: It has not been wiped with steel wool yet. Side A is rusty, but it does not look that deep. It should be cleaned and inspected then. Side B is fine. The orange areas are just surface “stains”, not pits.

Flywheel 8: $130 It has not been cleaned. Yet it’s clean and almost new. Notice side A where the points rub the hardest against the cam, where it’s shiny and dark (a reflection). That is the (opening) up ramp and the start of the plateau. Side B has no signs of wear, meaning that the points don’t rub very hard in that area.